Matcaps not showing up
it's not a problem of configuration, surely something will be damaged in your folder in .appdata where it hosts temporary blender configuration, I do not know if you use linux or windows, but I'll give you an example in windows that is the most common
you would have to delete that folder inside .appdata and restart blender, if the problem is solved it would be everything, but if the problem you got, it means that your blender is damaged, and it would be more difficult than you think to be doing a debug, my choice would be to reinstall blender cleanly, deleting all traces of the previous installation, that means using blichbit or ccelaner and eliminate what you find from blender in .appdata

NOTE: it is important that before doing all this, make a backup of all your addons that you have added, because when you delete this folder you will lose all
or you can make a list of the ones you have and download them once more